Eruption control in thermally stable pcd products

ABSTRACT

A method of making a polycrystalline diamond cutting element includes placing a body of polycrystalline diamond including a matrix phase of bonded together diamond grains and a plurality of empty interstitial spaces between the bonded together diamond grains adjacent a first substrate material to form an assembly and subjecting the assembly to high pressure/high temperature conditions that include an initial pressure ramping, a pressure hold, and a second pressure ramping.

CROSS-REFERENCE OF RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119, this application claims the benefit of U.S.Provisional Patent Application No. 61/730,305, filed on Nov. 27, 2012,which is herein incorporated by reference in its entirety.

BACKGROUND

Polycrystalline diamond (“PCD”) materials and PCD elements formedtherefrom are well known in the art. Conventional PCD may be formed bysubjecting diamond particles in the presence of a suitable solvent metalcatalyst material to processing conditions of high pressure/hightemperature (HPHT), where the solvent metal catalyst promotes desiredintercrystalline diamond-to-diamond bonding between the particles,thereby forming a PCD structure. The resulting PCD structure producesenhanced properties of wear resistance and hardness, making such PCDmaterials extremely useful in aggressive wear and cutting applicationswhere high levels of wear resistance and hardness are desired. FIG. 1illustrates a microstructure of conventionally formed PCD material 10including a plurality of diamond grains 12 that are bonded to oneanother to form an intercrystalline diamond matrix first phase. Thecatalyst/binder material 14, e.g., cobalt, used to facilitate thediamond-to-diamond bonding that develops during the sintering process isdispersed within the interstitial regions formed between the diamondmatrix first phase. The term “particle” refers to the powder employedprior to sintering a superabrasive material, while the term “grain”refers to discernable superabrasive regions subsequent to sintering, asknown and as determined in the art.

The catalyst/binder material used to facilitate diamond-to-diamondbonding can be provided generally in two ways. The catalyst/binder canbe provided in the form of a raw material powder that is pre-mixed withthe diamond grains or grit prior to sintering. In some cases, thecatalyst/binder can be provided by infiltration into the diamondmaterial (during high temperature/high pressure processing) from anunderlying substrate material that the final PCD material is to bebonded to. After the catalyst/binder material has facilitated thediamond-to-diamond bonding, the catalyst/binder material is generallydistributed throughout the diamond matrix within interstitial regionsformed between the bonded diamond grains. Particularly, as shown in FIG.1, the binder material 14 is not continuous throughout themicrostructure in the conventional PCD material 10. Rather, themicrostructure of the conventional PCD material 10 may have a uniformdistribution of binder among the PCD grains. Thus, crack propagationthrough conventional PCD material will often travel through the lessductile and brittle diamond grains, either transgranularly throughdiamond grain/binder interfaces 15, or intergranularly through thediamond grain/diamond grain interfaces 16.

Solvent catalyst materials may facilitate diamond intercrystallinebonding and bonding of PCD layers to each other and to an underlyingsubstrate. Solvent catalyst materials used for forming conventional PCDinclude metals from Group VIII of the Periodic table, such as cobalt,iron, or nickel and/or mixtures or alloys thereof, with cobalt being themost common. Conventional PCD may include from 85 to 95% by volumediamond and a remaining amount of the solvent catalyst material.However, while higher metal content increases the toughness of theresulting PCD material, higher metal content also decreases the PCDmaterial hardness, thus limiting the flexibility of being able toprovide PCD layers having desired levels of both hardness and toughness.Additionally, when variables are selected to increase the hardness ofthe PCD material, brittleness also increases, thereby reducing thetoughness of the PCD material.

PCD is commonly used in earthen drilling operations, for example incutting elements used on various types of drill bits. Although PCD isextremely hard and wear resistant, PCD cutting elements may still failduring normal operation. Failure may occur in three common forms, namelywear, fatigue, and impact cracking. The wear mechanism occurs due to therelative sliding of the PCD relative to the earth formation, and itsprominence as a failure mode is related to the abrasiveness of theformation, as well as other factors such as formation hardness orstrength, and the amount of relative sliding involved during contactwith the formation. Excessively high contact stresses and hightemperatures, along with a very hostile downhole environment, also tendto cause severe wear to the diamond layer. The fatigue mechanism(including both thermal and/or mechanical fatigue) involves theprogressive propagation of a surface crack, initiated on the PCD layer,into the material below the PCD layer until the crack length issufficient for spalling or chipping. Lastly, the impact mechanisminvolves the sudden propagation of a surface crack or internal flawinitiated on the PCD layer, into the material below the PCD layer untilthe crack length is sufficient for spalling, chipping, or catastrophicfailure of the cutting element.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

In one aspect, embodiments disclosed herein relate to a method of makinga polycrystalline diamond cutting element that includes placing a bodyof polycrystalline diamond including a matrix phase of bonded togetherdiamond grains and a plurality of empty interstitial spaces between thebonded together diamond grains adjacent a first substrate material toform an assembly and subjecting the assembly to high pressure/hightemperature conditions that include an initial pressure ramping, apressure hold, and a second pressure ramping.

In another aspect, embodiments disclosed herein relate to a method offorming a polycrystalline ultra-hard material that includes placing avolume of ultra-hard material adjacent to a substrate material includinga Group VIII-containing material to form an assembly, subjecting theassembly to a first high pressure/high temperature condition sufficientto cause the Group VIII-containing material to melt and partiallyinfiltrate the volume of ultra-hard material, and subjecting thecombination to a second high pressure/high temperature conditionsufficient to cause the Group VIII-containing material to furtherinfiltrate the volume of ultra-hard material, where the pressure of thesecond high pressure/high temperature condition is higher than that ofthe first high pressure/high temperature condition.

In yet another aspect, embodiments disclosed herein relate to apolycrystalline diamond compact that includes a polycrystalline diamondbody including a matrix phase of bonded together diamond grains and aplurality of interstitial spaces between the bonded together diamondgrains, where the polycrystalline diamond body is substantially free oferuptions, and a substrate attached to the polycrystalline diamond bodyat an interface, where the polycrystalline diamond body has at least tworegions, a first region adjacent the interface and a second regionopposite the interface, where the first region of the polycrystallinediamond body has an infiltrant material disposed within the interstitialspaces and being substantially free of a catalyst material used to formthe polycrystalline diamond body, and where the interstitial spaces inthe second region of the polycrystalline diamond body are substantiallyfree of the infiltrant material and the catalyst material used to formthe polycrystalline diamond body.

Other aspects and advantages of the claimed subject matter will beapparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present disclosure are described with reference tothe following figures. The same numbers are used throughout the figuresto reference like features and components.

FIG. 1 shows the microstructure of conventionally formed polycrystallinediamond.

FIG. 2 is a picture of a reinfiltrated PCD diamond table after removingthe metal matrix.

FIG. 3 is a picture of a reinfiltrated PCD diamond table, after removingthe metal matrix, formed according to embodiments of the presentdisclosure.

FIGS. 4.1-4.3 shows a schematic of formation of a cutting element inaccordance with the present disclosure.

FIG. 5 shows a fixed cutter drill bit.

FIG. 6 shows a hole opener.

FIG. 7 shows is a cross-sectional view of a conventionally formedreinfiltrated diamond compact.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein relate to use of multiplepressure stages during the formation of a polycrystalline diamondcompact cutter, and the polycrystalline diamond compact cutters formedby such processing.

Polycrystalline ultra-hard materials, and compacts formed therefrom, arespecifically engineered having a polycrystalline ultra-hard materialbody having a material microstructure that is substantially free ofsubstrate material eruptions, e.g., catalyst or infiltrant materialeruptions, and thereby free of localized concentrations, regions orvolumes of the catalyst or infiltrant material therein, andsubstantially free of any other substrate constituent material. As usedherein, “eruptions” refer to precipitated regions of carbide grains andbinder pools (catalyst or infiltrant material) formed from the substratematerial, which may create inclusions that are substantially larger thanthe interstitial regions formed in a polycrystalline diamond body.Eruptions created by binder pools may leave voids within the materialmicrostructure once the binder is removed. In other words, pores may notbe present in the reinfiltrated polycrystalline diamond body until thebinder pools are removed. Thus, “eruptions” may refer to inclusions orcollections of precipitated material different from the remainingpolycrystalline diamond microstructure, while “pores” refer to the voidsleft in the polycrystalline diamond microstructure after removal of theinclusions. As used herein, the eruptions may be at least an order ofmagnitude larger than conventional interstitial regions. Eruptions mayoccur during HPHT bonding methods of attaching a diamond body to asubstrate without pressure control, where the eruptions precipitate fromthe substrate into the diamond body.

For example, FIG. 7 shows an example of a diamond compact 400 formed byHPHT bonding of a preformed diamond body 410 to a tungsten carbidesubstrate 420 without using the pressure stages described herein. Duringthe HPHT step, eruptions 430 of tungsten carbide and cobalt precipitatedfrom the substrate 420 into the diamond body 410 in a branched pattern.Eruptions 430 occurring from the HPHT bonding process of attaching adiamond body 410 to a tungsten carbide substrate 420 are distinct fromsubstrate material that may infiltrate into the diamond body 410 duringthe HPHT bonding process to form the metallic bonds. For example, asdescribed above, eruptions 430 may be made of precipitated tungstencarbide and cobalt, which has a tree-like or dendrite form extendinginto the diamond body, and which may have a substantially larger sizethan the infiltrated materials residing in interstitial spaces betweendiamond grains bonded together. During the HPHT bonding process,substrate material may also infiltrate into the diamond body.Infiltration occurs when the temperature of the HPHT bonding processreaches the melting temperature of the substrate material. For example,when the HPHT bonding process temperature reaches the melting point ofcobalt, the cobalt from the tungsten carbide substrate may melt andinfiltrate into the diamond body, thereby filling at least a portion ofthe empty interstitial regions. Further, prior to attachment to thesubstrate, the diamond body 410 may include bonded together diamondgrains and substantially empty interstitial regions between the bondedtogether diamond grains. After the HPHT bonding process, the diamondbody 410 may have an amount of infiltrated cobalt disposed within theinterstitial regions. Further, the present disclosure also relates tothe use of a two-stage pressure profile during HPHT sintering andformation of polycrystalline diamond to result in a more uniformpolycrystalline diamond microcrystalline structure.

Eruptions may have a distinct form and composition from the remainingdiamond microstructure and may also produce a non-uniform substratemicrostructure. Thus, in accordance with the present disclosure, thecatalyst or infiltrant material in such polycrystalline ultra-hardmaterial body is instead evenly dispersed throughout the materialmicrostructure, or throughout at least a region of materialmicrostructure for those embodiments where the catalyst or infiltrantmaterial has been removed therefrom. In an example embodiment, suchpolycrystalline ultra-hard materials and compacts are formed bycontrolling the HPHT process used to sinter the polycrystallineultra-hard material, to regulate the manner in which the catalyst orinfiltrant material melts and is infiltrated into the adjacentultra-hard material before and during the sintering process.

For example, FIG. 2 shows an example of a conventional pre-formeddiamond table 200 that had been reinfiltrated with cobalt by HPHTprocessing without using a two-stage pressure profile. The diamond table200 has a plurality of pores 210 formed therein. Particularly, eruptionsof a metal matrix precipitated from a substrate into the diamond table200 during processing, and when the metal matrix material wassubsequently removed, the pores 210 were left in the diamond table 200.In other words, the pores 210 in the diamond table 200 are not formeduntil the metal matrix is removed, such as by leaching. In contrast,FIG. 3 shows a diamond table 300 formed according to methods of thepresent disclosure, where the preformed diamond table 300 had beenattached to a substrate (not shown) by HPHT bonding using a two-stagepressure. As shown, the diamond table 300 has a substantially continuousmicrostructure, where substantially no eruptions have been formed by thereinfiltration of cobalt.

Further, eruptions may create a non-uniform microstructure in thepolycrystalline diamond. Particularly, eruptions formed usingconventional methods of attaching a tungsten carbide substrate to adiamond body may include precipitated tungsten carbide grains and cobaltpools extending into the diamond body in a tree-shaped or branchedpattern. Thus, the attached polycrystalline diamond body may have amicrostructure including a plurality of bonded together diamond grains,a plurality of interstitial regions disposed among the bonded togetherdiamond grains, and extensions of precipitated tungsten carbide grainsand cobalt pools extending from the interface between the tungstencarbide substrate and diamond body a distance into the diamond body andthrough the bonded together diamond grains and interstitial regions.However, constructions formed according to methods of the presentdisclosure may have an attached diamond body that is substantially freeof eruptions. In other words, the attached diamond body may have asubstantially uniform microstructure including a plurality of bondedtogether diamond grains and a plurality of interstitial regions disposedamong the bonded together diamond grains.

Aspects of the present disclosure involve the use of an HPHT profilethat is controlled to minimize or reduce the number of eruptions of thesubstrate materials into the diamond body. The controlled HPHT processmay involve a process used in the initial formation of a polycrystallinediamond body on a substrate or/and it may involve a subsequent HPHTprocess whereby a previously formed polycrystalline diamond (PCD) bodyis attached to a substrate.

As used herein, the term “PCD” refers to polycrystalline diamond thathas been formed, at high pressure/high temperature (HPHT) conditions,through the use of a catalyst, such as solvent metal catalysts fromGroup VIII of the Periodic table, non-metallic catalysts includingcarbonates, as well as non-catalyst formed polycrystalline diamondformed with even higher temperatures and pressure than those used toform polycrystalline diamond with cobalt.

In accordance with particular embodiments of the present disclosure, thetwo-stage pressure profile of the HPHT process may be particularlyapplicable for attaching previously formed diamond bodies to a substratein an HPHT process to reduce or avoid the formation of eruptions withinthe diamond body. In such embodiments, the diamond body attached to thesubstrate may be previously treated to be rendered thermally stable sothat the diamond body is substantially free of the catalyst materialused to form the diamond body. When the diamond body is then attached toa substrate in an HPHT process, the bond is formed by a continuous metalbond. However, other embodiments of the present disclosure also relateto the use of a two-stage pressure profile in the HPHT process used toform the polycrystalline diamond microstructure.

Forming Polycrystalline Diamond

A polycrystalline diamond body may be formed in a conventional manner,such as by a high pressure, high temperature sintering of “green”particles to create intercrystalline bonding between the particles.“Sintering” may involve a high pressure, high temperature (HPHT)process. Examples of high pressure, high temperature (HPHT) process canbe found, for example, in U.S. Pat. Nos. 4,694,918; 5,370,195; and4,525,178. Briefly, to form the polycrystalline diamond object, anunsintered mass of diamond crystalline particles is placed within ametal enclosure of the reaction cell of a HPHT apparatus. A suitableHPHT apparatus for this process is described in U.S. Pat. Nos.2,947,611; 2,941,241; 2,941,248; 3,609,818; 3,767,371; 4,289,503;4,673,414; and 4,954,139. A metal catalyst, such as cobalt or otherGroup VIII metals, may be included with the unsintered mass ofcrystalline particles to promote intercrystalline diamond-to-diamondbonding. The catalyst material may be provided in the form of powder andmixed with the diamond grains, or may be infiltrated into the diamondgrains during HPHT sintering. For example, a minimum temperature may beabout 1200° C. (2192° F.) and a minimum pressure may be about 35kilobars. In some embodiments, processing may be conducted at a pressureof at least 45 kbar and 1300° C. (2372° F.). Those of ordinary skill inthe art will appreciate that a variety of temperatures and pressures maybe used, and the scope of the present invention is not limited tospecifically referenced temperatures and pressures. Further, it is alsowithin the scope of the present disclosure that the two-step pressureprofile disclosed below may be used in the polycrystalline diamondformation process.

Diamond grains useful for forming a polycrystalline diamond body mayinclude any type of diamond particle, including natural or syntheticdiamond powders having a wide range of grain sizes. For example, suchdiamond powders may have an average grain size in the range fromsubmicrometer in size to 100 micrometers, and from 1 to 80 micrometersin other embodiments. Further, one skilled in the art would appreciatethat the diamond powder may include grains having a mono- or multi-modaldistribution.

Moreover, the diamond powder used to prepare the PCD body may besynthetic diamond powder or natural diamond powder. Synthetic diamondpowder is known to include small amounts of solvent metal catalystmaterial and other materials entrained within the diamond crystalsthemselves. The diamond grain powder, whether synthetic or natural, maybe combined with or already includes a desired amount of catalystmaterial to facilitate desired intercrystalline diamond bonding duringHPHT processing. Suitable catalyst materials useful for forming the PCDbody include those solvent metals selected from the Group VIII of thePeriodic table, with cobalt (Co) being the most common, and mixtures oralloys of two or more of these materials. In a particular embodiment,the diamond grain powder and catalyst material mixture may include 85 to95% by volume diamond grain powder and the remaining amount catalystmaterial. In other embodiments, the diamond grain powder can be usedwithout adding a solvent metal catalyst in applications where thesolvent metal catalyst can be provided by infiltration during HPHTprocessing from the adjacent substrate or adjacent other body to bebonded to the PCD body.

The diamond powder may be combined with the desired catalyst material,and the reaction cell is then placed under processing conditionssufficient to cause the intercrystalline bonding between the diamondparticles. In the event that the formation of a PCD compact including asubstrate bonded to the PCD body is desired, a selected substrate isloaded into the container adjacent the diamond powder mixture prior toHPHT processing. Additionally, in the event that the PCD body is to bebonded to a substrate, and the substrate includes a metal solventcatalyst, the metal solvent catalyst used for catalyzingintercrystalline bonding of the diamond may be provided by infiltration,in which case, a metal solvent catalyst does not have to be mixed withthe diamond powder prior to HPHT processing.

In an example embodiment, the device is controlled so that the containeris subjected to a HPHT process including a pressure in the range of from40 to 70 kilobars and a temperature in the range of from about 1320 to1600° C., for a sufficient period of time. During this HPHT process, thecatalyst material in the mixture melts and infiltrates the diamond grainpowder to facilitate intercrystalline diamond bonding. During theformation of such intercrystalline diamond bonding, the catalystmaterial may migrate into the interstitial regions within themicrostructure of the so-formed PCD body that exists between the diamondbonded grains. It should be noted that if too much additionalnon-diamond material is present in the powdered mass of crystallineparticles, appreciable intercrystalline bonding is prevented during thesintering process. Such a sintered material where appreciableintercrystalline bonding has not occurred is not within the definitionof PCD. Following such formation of intercrystalline bonding, apolycrystalline diamond body may be formed that has, in one embodiment,at least about 80 percent by volume diamond, with the remaining balanceof the interstitial regions between the diamond grains occupied by thecatalyst material. In other embodiments, such diamond content mayinclude at least 85 percent by volume of the formed diamond body, and atleast 90 percent by volume in yet another embodiment. However, oneskilled in the art would appreciate that other diamond densities (orgradients of diamond densities) may be used in alternative embodiments.In particular embodiments, the polycrystalline diamond bodies beingleached in accordance with the present disclosure include what isfrequently referred to in the art as “high density” polycrystallinediamond, which refers to a diamond body having a diamond content of atleast 90 percent by volume. However, in other embodiments, the highdensity polycrystalline diamond used in the method of the presentdisclosure may have a density of at least 92 percent by volume up to 97percent by volume. One skilled in the art would appreciate thatconventionally, as diamond density increases, the leaching time (andpotential inability to effectively leach) similarly increases.

Further, one skilled in the art would appreciate that, frequently, adiamond layer is sintered to a carbide substrate by placing the diamondparticles on a preformed substrate in the reaction cell and sintering.However the present disclosure is not so limited. Rather, thepolycrystalline diamond bodies treated in accordance with the presentdisclosure may or may not be attached to a substrate.

In a particular embodiment, the polycrystalline diamond body is formedusing solvent catalyst material provided as an infiltrant from asubstrate, for example, a WC—Co substrate, during the HPHT process. Insuch embodiments where the polycrystalline diamond body is formed with asubstrate, it may be desirable to remove the polycrystalline diamondportion from the substrate prior to leaching so that leaching agents maycontact the diamond body in an unshielded manner, i.e., from each sideof the diamond body without substantial restriction.

In various embodiments, a formed PCD body having a catalyst material inthe interstitial spaces between bonded diamond grains is subjected to aleaching process (before or after attachment to a substrate), wherebythe catalyst material is removed from the PCD body. As used herein, theterm “removed” refers to the reduced presence of catalyst material inthe PCD body, and is understood to mean that a substantial portion ofthe catalyst material no longer resides in the PCD body. However, oneskilled in the art would appreciate that the leaching process is limitedin that trace amounts of catalyst material may still remain in themicrostructure of the PCD body within the interstitial regions and/oradhered to the surface of the diamond grains. Such trace amounts mayresult from limited access of leaching agents during the leachingprocess, and because of this limited access, alternative methods may beused to reduce the thermal coefficient differential between theremaining catalyst material and diamond.

Rather than actually removing the catalyst material remaining in theinterstitial spaces and/or adhered to the surface of the diamond grainsfrom the PCD body or compact, the selected region of the PCD body orcompact can be rendered thermally stable by treating the catalystmaterial in a manner that reduces or prevents the potential for thecatalyst material to adversely impact the intercrystalline bondeddiamond at elevated temperatures due to the thermal mismatch between thediamond and the remaining catalyst material as well as potential backconversion or graphitization. For example, the catalyst material can becombined chemically with another material or transformed into anothermaterial, thus causing it to no longer act as a catalyst material.Accordingly, as used herein, the terms “removing substantially all” or“substantially free” as used in reference to the catalyst material isintended to cover the different methods in which the catalyst materialcan be treated to no longer adversely impact the intercrystallinediamond in the PCD body or compact with increasing temperature.

The quantity of the catalyst material remaining in the material PCDmicrostructure after the PCD body has been subjected to a leachingtreatment may vary, for example, on factors such as the treatmentconditions, including treatment time, as well as whether the PCD body isattached to the substrate body before or after leaching. Further, oneskilled in the art would appreciate that it may be desired in certainapplications to allow a small amount of catalyst material to remain inthe PCD body. In a particular embodiment, the PCD body may include up to1-2 percent by weight of the catalyst material. However, one skilled inthe art would appreciate that the amount of residual catalyst present ina leached PCD body may depend on the diamond density of the material andbody thickness.

A conventional leaching process involves the exposure of an object to beleached with a leaching agent, such as described in U.S. Pat. No.4,224,380. In select embodiments, the leaching agent may be a weak,strong, or mixtures of acids. In other embodiments, the leaching agentmay be a caustic material such as NaOH or KOH. Suitable acids mayinclude, for example, nitric acid, hydrofluoric acid, hydrochloric acid,sulfuric acid, phosphoric acid, or perchloric acid, or combinations ofthese acids. In addition, caustics, such as sodium hydroxide andpotassium hydroxide, have been used to the carbide industry to digestmetallic elements from carbide composites. In addition, other acidic andbasic leaching agents may be used as desired. Those having ordinaryskill in the art will appreciate that the molarity of the leaching agentmay be adjusted depending on the time desired to leach, concerns abouthazards, etc.

Once the leaching step is completed and the PCD body is removed from theleaching agent, the resulting material microstructure of the leachedportion of the diamond body may include a first matrix phase of thebonded-together diamond grains and a second phase of a plurality ofempty interstitial regions dispersed within the matrix phase. In otherwords, at the end of the leaching process, the treated interstitialregions may be substantially empty so that the second phase may bedescribed as a plurality of voids or empty regions dispersed throughoutthe diamond-bonded matrix phase. Thus, the leached portion of thediamond body may be substantially free of the catalyst material used toinitially form or sinter the diamond body, and may be referred to asthermally stable polycrystalline diamond.

Reattachment

Preformed diamond bodies may be attached (or reattached) to a substratesubjecting the polycrystalline diamond body and substrate to the HPHTconditions disclosed herein, to facilitate attachment to a bit, cuttingtool, or other end use application or device. Furthermore, methods ofattaching (or reattaching) a diamond layer to a substrate may result inthe migration of an infiltrant material, the source of which may be thesubstrate and/or an optional intermediate material. In a particularembodiment, the source of infiltrant material may be a substrate that isattached to preformed diamond body during the HPHT process.

As used herein, the term “infiltrant material” is understood to refer tomaterials that are other than the catalyst material used to initiallyform the diamond body, and may include materials identified in GroupVIII of the periodic table that have subsequently been introduced intothe already formed diamond body. The type of infiltrant material is nota limitation on the scope of the present disclosure. Additionally, theterm “infiltrant material” is not intended to be limiting on theparticular method or technique used to introduce such material into thealready formed diamond body. The infiltrant material may be selectedfrom the group of materials including metals, ceramics, cermets, orcombinations thereof. In an example embodiment, the infiltrant materialis a metal or metal alloy selected from Group VIII of the PeriodicTable, such as cobalt, nickel, iron or combinations thereof. It is to beunderstood that the choice of material or materials used as theinfiltrant material can and will vary depending on such factorsincluding but not limited to the end-use application, and the type anddensity of the diamond grains used to form the polycrystalline diamondmatrix first phase, and the mechanical properties and/or thermalcharacteristics desired for the polycrystalline diamond construction.

After forming a diamond body, the catalyst material residing in theinterstitial regions may be removed so that an infiltrant material maytake its place in the interstitial regions. That is, once the catalystmaterial used to initially form the diamond body is removed from thediamond body, the remaining microstructure includes a polycrystallinematrix phase with a plurality of interstitial voids forming what isessentially a porous material microstructure.

The voids or pores in the polycrystalline diamond body may be filledwith the infiltrant material using a number of different techniques.Further, voids throughout the diamond body or voids throughout a portionof the diamond body may be filled with the replacement material. In anexample embodiment, the infiltrant material may be introduced into thediamond body by liquid-phase sintering under HPHT conditions. In suchexample embodiment, the infiltrant material may be provided in the formof a sintered part or a green-state part that contains the infiltrantmaterial and that is positioned adjacent one or more surfaces of thediamond body. The assembly is placed into a container that is subjectedto HPHT conditions sufficient to melt the infiltrant material within thesintered part or green-state part and cause it to infiltrate into thediamond body. In an example embodiment, the source of the infiltrantmaterial may be a substrate that will be used to form a compact from thepolycrystalline diamond construction by attachment to the diamond bodyduring the HPHT process.

The term “filled”, as used herein to refer to the presence of theinfiltrant material in the voids or pores of the diamond body thatresulted from removing the catalyst material used to form the diamondbody therefrom, is understood to mean that a substantial volume of suchvoids or pores contain the infiltrant material. However, it is to beunderstood that there may also be a volume of voids or pores within thesame region of the diamond body that do not contain the infiltrantmaterial, and that the extent to which the infiltrant materialeffectively displaces the empty voids or pores will depend on suchfactors as the particular microstructure of the diamond body, theeffectiveness of the process used for introducing the infiltrantmaterial, and the desired mechanical and/or thermal properties of theresulting polycrystalline diamond construction. In some embodiments,when introduced into the diamond body, the infiltrant fillssubstantially all of the voids or pores throughout the diamond body. Insome embodiments, complete migration of the infiltrant material throughthe diamond body is not realized, in which case a region of the diamondbody may not include the infiltrant material. This region devoid of theinfiltrant material from such incomplete migration may extend from theregion including the infiltrant to a surface portion of the diamondbody, such as a cutting surface of the diamond body.

In an example embodiment, a substrate is used as the source of theinfiltrant material and to form the polycrystalline construction.Substrates useful in this regard may include substrates that are used toform conventional PCD, e.g., those formed from metals, ceramics, and/orcermet materials that contain a desired infiltrant. In an exampleembodiment, the substrate is formed from WC—Co, and is positionedadjacent the diamond body after the metal catalyst material used toinitially form the same been removed, and the assembly is subjected toHPHT conditions sufficient to cause the cobalt in the substrate to meltand infiltrate into and fill the voids or pores in the polycrystallinediamond matrix.

Once the diamond body has been filled with the infiltrant material, itmay then be treated to remove a portion of the infiltrant materialtherefrom. In some embodiments, where the infiltrant material did notmigrate completely through the diamond body, a subsequent infiltrantremoval step may not be conducted, or may useful as a clean up processto ensure a uniform infiltrant removal depth. Treating the compact toremove such infiltrant material may render the polycrystalline diamondbody or compact thermally stable by treating the infiltrant material ina manner that reduces or prevents the potential for the infiltrantmaterial to adversely impact the intercrystalline bonded diamond atelevated temperatures. Generally, infiltrant materials are problematicwhen heat is generated at the cutter impact point of the compact.Specifically, heat generated at the exposed part of the polycrystallinediamond body, caused by friction between the polycrystalline diamond andthe work material, may result in thermal damage to the polycrystallinediamond in the form of cracks (due to differences in thermal expansioncoefficients) which may lead to spalling of the polycrystalline diamondlayer, delamination between the polycrystalline diamond and thesubstrate, and back conversion of diamond to graphite causing rapidabrasive wear. Thus, increased thermal stability may be achieved bytreating the compact to remove such infiltrant material using suchmethods as leaching or other methods known in the art.

In an example embodiment, the infiltrant material is removed from thediamond body a depth of less than about 0.7 mm from the desired surfaceor surfaces, and in some embodiments, in the range of from about 0.05 to0.5 mm. Ultimately, the specific depth of the region formed in thediamond body by removing the infiltrant material will vary depending onthe particular end-use application.

In some embodiments, a detached polycrystalline diamond layer may betreated to first remove the catalyst material initially used to form thepolycrystalline bonds in the polycrystalline diamond layer. Theresulting thermally stable polycrystalline diamond body may then beattached to a substrate using an HPHT process for a period of time andat a temperature sufficient to meet the melting point of an infiltrantmaterial present in the substrate such that the infiltrant materialmigrates to the polycrystalline diamond body. The resultingpolycrystalline diamond compact may then be treated to remove a portionof the infiltrant material therefrom. Techniques useful for removing aportion of the infiltrant material from the diamond compact include thesame techniques described above for removing the catalyst material usedto initially form the diamond compact from the polycrystalline diamondbody, e.g., such as by leaching or the like. Depending on theapplication, it may be desired that the process of removing theinfiltrant material be controlled so that the infiltrant material beremoved from a targeted region of the diamond compact extending adetermined depth from one or more diamond compact surfaces. Thesesurfaces may include working and/or nonworking surfaces of the diamondcompact.

Referring now to FIGS. 4.1-4.3 collectively, an embodiment of theprocess steps of the present disclosure is shown. As shown in FIG. 4.1,a polycrystalline diamond body 30 having a catalyzing material found inthe interstitial regions between the diamond grains (as described above)may be formed attached to a carbide substrate 34. The polycrystallinediamond body 30 may be detached (shown in FIG. 4.2) from the substrate34 simultaneous with or prior to removal of the catalyzing material fromthe interstitial spaces. Further, as shown in FIG. 4.3, the diamond body30 may then be attached (or reattached) to a substrate 36 throughsintering, and in particular using multiple stages of elevated pressure.

Two Stage Pressure Profile

In accordance with embodiments of the present disclosure, the HPHTprocess in which the diamond material (either preformed body or mass ofdiamond particles) is attached to a substrate and infiltrated with acatalyst or infiltrant material, may include a two-stage pressureprofile. The first stage may include elevated temperatures (totemperatures sufficient to cause infiltration of the catalyst orinfiltrant material), and a first stage of pressure ramping. However,after a short hold at the first stage of elevated pressure, the pressureis further ramped to a predetermined second stage pressure and held forthe duration of the HPHT process. In one or more embodiments, the secondpressure hold may be longer than the first pressure hold. Further, inone or more embodiments, the first pressure ramping is at a greater ramprate than the second pressure ramping. Suitable ramp rates for the firstpressure ramping (of the internal cell pressure increase) may includerates of 0.8 to 15 kbar/sec, and at least about 1, 2, 3, or 5 kbar/secin one or more embodiments, and no more than about 14, 13, 10, or 8kbar/sec in one or more embodiments, where any lower limit may be usedin combination with any upper limit. Suitable ramp rates for the secondpressure ramping may include rates of may include rates of 0.8 to 15kbar/sec, and at least about 1, 1.2, 1.5, or 2 kbar/sec in one or moreembodiments, and no more than about 6, 5, 4, or 3 kbar in one or moreembodiments, where any lower limit may be used in combination with anyupper limit. As mentioned above, these pressure ramp rates are the ramprates for the internal cell pressure experienced by the diamond body,etc., not the external application of hydraulic pressure applied thatwill trigger internal cell pressure increases. The correlation betweenthe hydraulic pressure applied and the internal cell pressure will varyfor each cell configuration, as understood by those of ordinary skill inthe art, and thus, because the internal cell pressure is what effectsthe infiltration process as it is the pressure experienced by the cellcontents, it is the internal cell pressure that is discussed herein.

Further, suitable hold periods for the first pressure hold may rangefrom about 20 seconds to up to 240 seconds, and may be less than 120seconds or 60 seconds in particular embodiments, and suitable holdperiods for the second pressure hold may range from about 40 seconds upto 320 seconds, but may be less than 240 seconds or 180 seconds inparticular embodiments. It is also within the scope of the presentdisclosure that subsequent pressure stages may be reached in furtherstep-wise fashion.

The temperature reached during the two-stage HPHT process may range, forexample, from 1300 to 1600° C., but also may depend on the meltingtemperature of the infiltrant material selected. The total pressurerange for the two-stage HPHT process may generally range from at least40 kbar to 85 kbar, where the first pressure stage may range from 50kbar to 65 kbar in one or more embodiments, (e.g., 57 kbar), and thesecond pressure stage may range from 60 kbar to 82 kbar in one or moreembodiments. In one or more embodiments, the first pressure stage mayhave a lower limit of any of 40, 45, 50, 55, or 60 kbar, and an upperlimit of any of 50, 55, 60, 65, or 68 kbar, where any lower limit can beused in combination with any upper limit. Further, in one or moreembodiments, the second pressure stage may have a lower limit of any of55, 60, 65, or 70 kbar, and an upper limit of any of 60, 65, 70, 75, 80,or 82 kbar, where any lower limit can be used in combination with anyupper limit.

Further, like the ramp-hold-ramp pattern in the pressure increase, theHPHT conditions may also include an initial temperature ramping, atemperature hold, and a second temperature ramping, in one embodiment.In another embodiment, the high pressure/high temperature conditions mayinclude a monotonic increase in temperature through the initial pressureramping, the pressure hold, and the second pressure ramping. In yetanother embodiment, the high pressure/high temperature conditions mayinclude an initial temperature ramping during the initial pressureramping and a temperature hold through the pressure hold and secondpressure ramping. In one or more embodiments, a substantial majority ofthe temperature increase may occur during the first pressure ramping,where the second stage observes a temperature increase of less than 100degrees, less than 75 degrees, less than 50 degrees, less than 25degrees, or less than 20 degrees Celsius.

The cutting elements of the present disclosure may be incorporated invarious types of cutting tools, including for example, as cutters infixed cutter bits or on borehole enlargement tools such as reamers.Thus, the structure on which the cutting elements of the presentdisclosure may be installed may be referred to as a cutting elementsupport structure, i.e., a blade for fixed cutter bit or a reamer.

Referring now to FIG. 5, an embodiment of a fixed cutter drill bit 100is shown. As shown in FIG. 5, drill bit 100 includes a bit body 110having a threaded upper pin end 111 and a cutter face 112. The cutterface 112 may include a plurality of ribs or blades 120 arranged aboutthe rotational axis L of the drill bit and extending radially outwardfrom the bit body 110. Cutting elements, or cutters, 150 are embedded inthe blades 120 at predetermined angular orientations and radiallocations relative to a working surface and with a desired back rakeangle and side rake angle against a formation to be drilled. Cutters 150are conventionally attached to a drill bit or other downhole tool by abrazing process so that the ultra hard cutting table faces into thedirection of rotation of the bit. In the brazing process, a brazematerial is positioned between the cutter substrate and the cutterpocket. The material is melted and, upon subsequent solidification,bonds (attaches) the cutter in the cutter pocket.

A plurality of orifices 116 are positioned on the bit body 110 in theareas between the blades 120, which may be referred to as “gaps” or“fluid courses.” The orifices 160 are commonly adapted to acceptnozzles. The orifices 160 allow drilling fluid to be discharged throughthe bit in selected directions and at selected rates of flow between theblades 120 for lubricating and cooling the drill bit 100, the blades 120and the cutters 150. The drilling fluid also cleans and removes thecuttings as the drill bit 100 rotates and penetrates the geologicalformation. Without proper flow characteristics, insufficient cooling ofthe cutters 150 may result in cutter failure during drilling operations.The fluid courses are positioned to provide additional flow channels fordrilling fluid and to provide a passage for formation cuttings to travelpast the drill bit 100 toward the surface of a wellbore (not shown).

FIG. 6 shows a general configuration of a hole opener 830 that includesone or more cutting elements of the present disclosure. The hole opener830 includes a tool body 832 and a plurality of blades 838 disposed atselected azimuthal locations about a circumference thereof. The holeopener 830 generally includes connections 834, 836 (e.g., threadedconnections) so that the hole opener 830 may be coupled to adjacentdrilling tools that include, for example, a drillstring and/or bottomhole assembly (BHA) (not shown). The tool body 832 generally includes abore therethrough so that drilling fluid may flow through the holeopener 830 as it is pumped from the surface (e.g., from surface mudpumps (not shown)) to a bottom of the wellbore (not shown). The toolbody 832 may be formed from steel or from other materials known in theart. For example, the tool body 832 may also be formed from a matrixmaterial infiltrated with a binder alloy.

The blades 838 shown in FIG. 6 are spiral blades and are generallypositioned at substantially equal angular intervals about the perimeterof the tool body so that the hole opener 830. This arrangement is not alimitation on the scope of the invention, but rather is used merely toillustrative purposes. Those having ordinary skill in the art willrecognize that any downhole cutting tool may be used.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from this invention. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents, but alsoequivalent structures. Thus, although a nail and a screw may not bestructural equivalents in that a nail employs a cylindrical surface tosecure wooden parts together, whereas a screw employs a helical surface,in the environment of fastening wooden parts, a nail and a screw may beequivalent structures. It is the express intention of the applicant notto invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of theclaims herein, except for those in which the claim expressly uses thewords ‘means for’ together with an associated function.

What is claimed:
 1. A method of making a polycrystalline diamond cuttingelement, comprising: placing a body of polycrystalline diamondcomprising a matrix phase of bonded together diamond grains and aplurality of empty interstitial spaces between the bonded togetherdiamond grains adjacent a first substrate material to form an assembly;and subjecting the assembly to high pressure/high temperature conditionsthat include an initial pressure ramping, a pressure hold, and a secondpressure ramping.
 2. The method of claim 1, further comprising: placinga plurality of diamond particles adjacent a second substrate materialcomprising a catalyst material; subjecting the plurality of diamondparticles and the second substrate material to second hightemperature/high pressure conditions to form a polycrystalline diamondbody comprising a matrix phase of bonded together diamond grains and aplurality of interstitial spaces between the bonded together diamondgrains occupied by the catalyst material bonded to the second substratematerial; removing the second substrate material from thepolycrystalline diamond body; and removing substantially all of thecatalyst material from the interstitial spaces of the polycrystallinediamond body.
 3. The method of claim 1, wherein the high pressure/hightemperature conditions include an initial temperature ramping, atemperature hold, and a second temperature ramping.
 4. The method ofclaim 1, wherein the high pressure/high temperature conditions include amonotonic increase in temperature through the initial pressure ramping,the pressure hold, and the second pressure ramping.
 5. The method ofclaim 1, wherein the high pressure/high temperature conditions includean initial temperature ramping during the initial pressure ramping and atemperature hold through the pressure hold and second pressure ramping.6. The method of claim 1, wherein the high pressure/high temperatureconditions further include a second pressure hold following the secondpressure ramping.
 7. The method of claim 6, wherein the second pressurehold is longer than the first pressure hold.
 8. The method of claim 1,wherein the first pressure ramping is at a greater ramp rate than thesecond pressure ramping.
 9. The method of claim 1, wherein the firstpressure ranges from about 50 to 70 kbar.
 10. The method of claim 1,wherein the second pressure ranges from 70 to 82 kbar.
 11. The method ofclaim 1, wherein the first substrate material comprises a plurality ofcarbide particles bonded together by a infiltrant material.
 12. Themethod of claim 11, wherein during the subjecting step, the infiltrantmaterial infiltrates into at least some of the empty interstitialspaces.
 13. The method of claim 12, further comprising: removing atleast a portion of the infiltrant materials from the interstitialspaces.
 14. A method of forming a polycrystalline ultra-hard material,comprising: placing a volume of ultra-hard material adjacent to asubstrate material comprising a Group VIII-containing material to forman assembly; subjecting the assembly to a first high pressure/hightemperature condition sufficient to cause the Group VIII-containingmaterial to melt and partially infiltrate the volume of ultra-hardmaterial; and subjecting the combination to a second high pressure/hightemperature condition sufficient to cause the Group VIII-containingmaterial to further infiltrate the volume of ultra-hard material, thepressure of the second high pressure/high temperature condition ishigher than that of the first high pressure/high temperature condition.15. The method of claim 14, wherein the volume of ultra-hard materialcomprises a body of polycrystalline diamond comprising a matrix phase ofbonded together diamond grains and a plurality of empty interstitialspaces between the bonded together diamond grains.
 16. The method ofclaim 14, wherein the first high pressure/high temperature condition hasa temperature maximum that is substantially the same as the second highpressure/high temperature condition.
 17. The method of claim 14, furthercomprising: holding the first high pressure/high temperature conditionfor a period of time prior to ramping to the second high pressure/hightemperature condition.
 18. The method of claim 14, wherein the volume ofultra-hard material comprises a mass of diamond particles.
 19. Themethod of claim 14, further comprising: placing a plurality ofultra-hard particles adjacent a second substrate material comprising acatalyst material; subjecting the plurality of ultra-hard particles andthe second substrate material to second high temperature/high pressureconditions to form the ultrahard material comprising a matrix phase ofbonded together ultra-hard particle grains and a plurality ofinterstitial spaces between the bonded together ultra-hard particlegrains occupied by the catalyst material bonded to the second substratematerial; removing the second substrate material from thepolycrystalline diamond body; and removing substantially all of thecatalyst material from the interstitial spaces of the ultra-hardmaterial.
 20. A polycrystalline diamond compact, comprising: apolycrystalline diamond body comprising a matrix phase of bondedtogether diamond grains and a plurality of interstitial spaces betweenthe bonded together diamond grains, the polycrystalline diamond bodybeing substantially free of eruptions; and a substrate attached to thepolycrystalline diamond body at an interface, the polycrystallinediamond body comprising at least two regions, a first region adjacentthe interface and a second region opposite the interface, the firstregion of the polycrystalline diamond body comprising an infiltrantmaterial disposed within the interstitial spaces and being substantiallyfree of a catalyst material used to form the polycrystalline diamondbody, and the interstitial spaces in the second region of thepolycrystalline diamond body being substantially free of the infiltrantmaterial and the catalyst material used to form the polycrystallinediamond body.
 21. A cutting tool, comprising: at least onepolycrystalline diamond compact of claim 20 disposed thereon.